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From "Apache Spark (JIRA)" <>
Subject [jira] [Assigned] (SPARK-5905) Note requirements for certain RowMatrix methods in docs
Date Sat, 19 Sep 2015 11:18:05 GMT


Apache Spark reassigned SPARK-5905:

    Assignee:     (was: Apache Spark)

> Note requirements for certain RowMatrix methods in docs
> -------------------------------------------------------
>                 Key: SPARK-5905
>                 URL:
>             Project: Spark
>          Issue Type: Documentation
>          Components: Documentation, MLlib
>    Affects Versions: 1.3.0
>            Reporter: Xiangrui Meng
>            Priority: Trivial
> From mbofb's comment in PR
> {code}
> The description of RowMatrix.computeSVD and mllib-dimensionality-reduction.html should
be more precise/explicit regarding the m x n matrix. In the current description I would conclude
that n refers to the rows. According to
this way of describing a matrix is only used in particular domains. I as a reader interested
on applying SVD would rather prefer the more common m x n way of rows x columns (e.g.
) which is also used in (and also within
the ARPACK manual:
> “
> N Integer. (INPUT) - Dimension of the eigenproblem. 
> NEV Integer. (INPUT) - Number of eigenvalues of OP to be computed. 0 < NEV < N.

> NCV Integer. (INPUT) - Number of columns of the matrix V (less than or equal to N).
> “
> ).
> description of RowMatrix.computeSVD and mllib-dimensionality-reduction.html:
> "We assume n is smaller than m." Is this just a recommendation or a hard requirement.
This condition seems not to be checked and causing an IllegalArgumentException – the processing
finishes even though the vectors have a higher dimension than the number of vectors.
> description of RowMatrix. computePrincipalComponents or RowMatrix in general:
> I got a Exception.
> java.lang.IllegalArgumentException: Argument with more than 65535 cols: 7949273
> at org.apache.spark.mllib.linalg.distributed.RowMatrix.checkNumColumns(RowMatrix.scala:131)
> at org.apache.spark.mllib.linalg.distributed.RowMatrix.computeCovariance(RowMatrix.scala:318)
> at org.apache.spark.mllib.linalg.distributed.RowMatrix.computePrincipalComponents(RowMatrix.scala:373)
> This 65535 cols restriction would be nice to be written in the doc (if this still applies
in 1.3).
> {code}

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